Masetti Marco, Poli Simone, Sterlacchini Simone, Beretta Giovanni P, Facchi Arianna
Department of Earth Sciences, "Ardito Desio", University of Milan, Via Mangiagalli 34, 20133 Milan, Italy.
J Environ Manage. 2008 Jan;86(1):272-81. doi: 10.1016/j.jenvman.2006.12.023. Epub 2007 Feb 12.
The weights of evidence (WofE) modeling technique has been used to analyze both natural and anthropogenic factors influencing the occurrence of high nitrate concentrations in groundwater resources located in the central part of the Po Plain (Northern Italy). The proposed methodology applied in the Lodi District combines measurements of nitrate concentrations, carried out by means of a monitoring net of 69 wells, with spatial data representing both categorical and numerical variables. These variables describe either potential sources of nitrate and the relative ease with which it may migrate towards groundwater. They include population density, nitrogen fertilizer loading, groundwater recharge, soil protective capacity, vadose zone permeability, groundwater depth, and saturated zone permeability. Once conditional dependence problems among factors have been solved and validation tests performed, the statistical approach has highlighted negative and positive correlations between geoenvironmental factors and nitrate concentration in groundwater. These results have been achieved analysing the calculated statistical parameters (weights, contrasts, normalized contrasts) of each class by which each factor has been previously subdivided. This has permitted to outline: the overall influence each factor has on the presence/absence of nitrate; the range of their values mostly influencing this presence/absence; the most and least critical combination of factor classes existing in each specific zone; areas where the influence of impacting factor classes is reduced by the presence of not impacting factor classes. This last aspect could represent an important support for a correct land use management to preserve groundwater quality.
证据权重（WofE）建模技术已被用于分析影响意大利北部波河平原中部地下水资源中高硝酸盐浓度出现的自然和人为因素。在洛迪区应用的拟议方法将通过69口井的监测网络进行的硝酸盐浓度测量与代表分类变量和数值变量的空间数据相结合。这些变量描述了硝酸盐的潜在来源以及它向地下水迁移的相对难易程度。它们包括人口密度、氮肥施用量、地下水补给、土壤保护能力、包气带渗透率、地下水位深度和饱和带渗透率。一旦解决了因素之间的条件依赖问题并进行了验证测试，统计方法就突出了地质环境因素与地下水中硝酸盐浓度之间的负相关和正相关。这些结果是通过分析每个因素先前细分的每个类别的计算统计参数（权重、对比度、归一化对比度）而获得的。这使得能够概述：每个因素对硝酸盐存在与否的总体影响；其值的范围对这种存在与否的影响最大；每个特定区域中存在的因素类别的最关键和最不关键组合；由于非影响因素类别的存在而降低影响因素类别的影响的区域。最后这一方面可以为正确的土地利用管理以保护地下水质量提供重要支持。
